Fuelled the previous week, the two 715 kg satellites were carefully lowered and attached to the dispenser structure in turn.

The process during 27–28 August in the space centre’s 3SB preparation building went smoothly. To avoid any snags, the Galileos had previously undergone a ‘fit check’ with the dispenser at the very start of the launch campaign in late July.

The dispenser, custom-designed to hold Galileo pairs for Arianespace by Ruag Space Sweden, will carry the satellites for a total of 3 hr 48 min during ascent to the medium-altitude orbit.

Then, once the Fregat upper stage reaches the set 23 222 km altitude and 57.394° inclination, the dispenser performs its second crucial role: firing a pyrotechnic separation system to release them in opposing directions.

The next major step in the launch campaign is to attach the combined satellites plus dispenser to Fregat, which arrived in the 3SB building on Tuesday, 2 September, already fuelled and ready.

Once attached, the satellites plus Fregat will then be encapsulated within the launcher fairing, after which this ‘upper composite’ can then be attached to the other three stages of the Soyuz ST-B.

As much a spacecraft as a launcher stage, the reignitable Fregat will take the Galileos the bulk of the way to their designated orbit once the first three stages of the Soyuz achieve low orbit, some 9 min 24 sec after launch. A pair of Fregat firings will be separated by a 3 hr 13 min coast.

This latest Galileo launch campaign began with the arrival of the satellites in French Guiana on 24 July.

Two further satellites are scheduled for launch by end of this year. One is under test at ESA’s ESTEC technical centre in Noordwijk, the Netherlands, while the other has already completed its checks and is awaiting transportation to Kourou in the second half of October.

In addition, the first satellite of the following batch (Galileo 13) has arrived at ESTEC and is undergoing its thermal–vacuum test. The next will arrive by mid-September.